Paint planning guide

Paint estimates depend on surface area, coverage rate, number of coats, and how much paint is lost to texture, roller loading, touch-ups, and cutting in. A smooth new wall usually behaves differently from rough masonry, bare timber, or a heavily patched surface.

Use this calculator to turn room or surface measurements into a practical container estimate. It works best when you measure each wall or surface group, subtract large openings, and use the coverage rate printed on the paint label.

Before choosing cans

• Check whether the label coverage is for one coat or a complete system.
• Add extra allowance for porous, dark, textured, or previously unsealed surfaces.
• Keep primer, topcoat, ceiling paint, and trim paint as separate estimates.
• Buy enough from the same batch when color consistency matters.

The calculator gives a purchase starting point, but final coverage should be checked against the coating system recommended by the paint manufacturer.

Worked example

A room with a 4 m by 3 m footprint and 2.4 m walls has a 14 m perimeter and about 33.6 m² of wall surface. Deducting a 1.8 m² door leaves 31.8 m². Two coats create 63.6 m² of coverage; at 12 m² per litre that is about 5.3 litres, so two 4-litre cans provide a practical whole-container estimate.